Islamic State issues video of beheading of second US journalist

A masked Islamic State militant speaks next to a man purported to be US journalist Steven Sotloff at an unknown location in this still image from an undated video posted on a social media website.

The Islamic State militant group has released a video purporting to show the beheading of a second American hostage, journalist Steven Sotloff, raising the stakes in its confrontation with Washington over US air strikes on its insurgents in Iraq.

A masked figure in the video also issued a threat against a British hostage, a man the group named as David Haines, and warned governments to back off "this evil alliance of America against the Islamic State".

A statement released by Sotloff's family through a spokesman indicated the family considered the video to be authentic. "The family knows of this horrific tragedy and is grieving privately. There will be no public comment from the family during this difficult time," family spokesman Barak Barfi said.

The purported executioner appeared to be the same British-accented man who appeared in an Aug. 19 video showing the killing of American journalist James Foley, and it showed a similar desert setting. In both videos, the captives wore orange jumpsuits.

In Washington, the White House said it could not immediately confirm the authenticity of the video of Sotloff's beheading. But several US government sources said it appeared to be authentic.

Sotloff, a 31-year-old freelance journalist from Florida, was kidnapped in Syria in August 2013.

"I'm back, Obama, and I'm back because of your arrogant foreign policy towards the Islamic State, because of your insistence on continuing your bombings and in Amerli, Zumar and the Mosul Dam, despite our serious warnings," the masked man said in the video, addressing US President Barack Obama.

"So just as your missiles continue to strike our people, our knife will continue to strike the necks of your people."

In the video, Sotloff describes himself as "paying the price" with his life for the US intervention in Iraq.

In the video it released last month, Islamic State said Foley's death was in retaliation for US air strikes on its insurgents who have overrun wide areas of northern Iraq.

The United States resumed air strikes in Iraq in August for the first time since the withdrawal of the final US troops from the country in 2011.

The raids followed major gains by Islamic State, which has declared an Islamic Caliphate in areas it controls in Syria and Iraq.

"We have seen a video that purports to be the murder of US citizen Steven Sotloff by the Islamic State of Iraq and the Levant. The intelligence community is working as quickly as possible to determine its authenticity," White House National Security Council spokeswoman Bernadette Meehan said in a statement.

"If genuine, we are appalled by the brutal murder of an innocent American journalist and we express our deepest condolences to his family and friends. We will provide more information when it is available."